Cigarette smoking is believed to contribute to or cause roughly 30% of all cancer deaths. Cigarette smoke contains more than 3500 chemicals, at least 50 of which are carcinogens. Carbonyls, including acetaldehyde, acrolein (propenal), formaldehyde, and others, are formed through the pyrolysis of tobacco. Accordingly, these compounds are among the compounds present at high levels in cigarette smoke. In fact, acetaldehyde and acrolein are present in international brands of cigarettes at concentrations of 860 and 83 μg/mg of nicotine, respectively. The Scientific Basis of Tobacco Product Regulation, WHO Technical Report Series 951, World Health Organization, Geneva, Switzerland, 2008. Long-term exposure to formaldehyde, acrolein, and acetaldehyde is known to increase the risk of asthma and cancer.
Cigarette smoke and tar also contain other carcinogens, such as polycyclic aromatic alcohols, which initiate the formation of cancer. Co-carcinogens in cigarette smoke, such as phenols, have also been identified; co-carcinogens accelerate the production of cancer by other initiators. Many phenols, naphthols and other co-carcinogens are also irritants.
The World Health Organization (WHO) has recommended mandated lowering of allowable levels of these toxicants in cigarettes. Current methods of reducing the amount of a toxicant in cigarette smoke include incorporation of transition metal oxide clusters, such as clusters of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and oxides and mixtures thereof. The nano-sized clusters or nanoparticles of metal oxide are capable of catalyzing the conversion (oxidation) of carbon monoxide (CO) to carbon dioxide (CO2), or adsorbing carbon monoxide itself. The clusters are incorporated into a component of a smoking article, wherein the component is selected from the group consisting of tobacco cut filler, cigarette paper and cigarette filter material. See U.S. Pat. No. 7,712,471, incorporated herein by reference in its entirety. However, this reference not disclose any methods for reducing the levels of toxicants other than CO in the cigarette smoke.
Another method of reducing toxicants in cigarette smoke is disclosed in U.S. Pat. No. 6,615,843, hereby incorporated by reference in its entirety. This patent discloses a tobacco smoke filter synergistic composition comprised of antioxidants, such as ascorbic or citric acid, butylparaben, glutathione, melatonin, resveratrol, selenium, ubiquinones, or green tea, and adsorptive “minerals,” such as activated carbon, clinoptilolite, cuprous chloride, and ferrite. The antioxidants are effective as scavengers in reducing free radicals from the cigarette smoke, while activated carbon or similar adsorbent ‘minerals’ adsorb substantial levels of volatiles. However, U.S. Pat. No. 6,615,843 does not disclose any catalytic conversion of the volatile carbonylic compounds or phenols into less volatile chemicals. No catalytic condensation reactions of phenols and aldehydes found as toxicants in the cigarette smoke were disclosed.
Separately, metal-organic frameworks (MOF), constituted by metal ions or metal ion clusters occupying nodal framework positions coordinated with di- or multi-podal organic ligands, are rapidly emerging as an important family of crystalline materials to be utilized as catalysts in organic reactions. Some of these MOFs are crystalline materials with the lowest framework densities and the highest pore volume known to date. Among over 10,000 MOF materials, there are several transition-metal MOFs that are stable under liquid-phase reaction conditions. These include mesoporous chromium (III) terephthalate (MIL-101), which possesses acceptable resistance to water, common solvents, and temperatures (up to 320° C.). MIL-101 has a rigid zeotype crystal structure, consisting of 2.9 and 3.4-nm quasi-spherical cages accessible through windows of ca. 1.2 and 1.6 nm, respectively. Due to the high stability, MIL-101 exhibits no detectable leaching of chromium into solutions, allowing its safe use in different applications. In addition, MIL-101 possess a high density of chromium ions (three per elementary cell) with Lewis acid properties, which can be stable under reaction conditions. The open-pore structure of MIL-101 can be further functionalized by Pd or Au nanoparticles and polyoxometalate (POM) anions. The resulting composite materials are effective catalysts for hydrogenation reactions and oxidation reactions. Another POM material that can be utilized to functionalize the MIL-101 framework is phosphotungstic acid (PTA). PTA is the strongest known heteropolyacid. MIL-101/PTA composite materials (MIL101/PTA) have been shown to catalyze (i) the oxidation on of alkenes using molecular oxygen and aqueous hydrogen peroxide as oxidants, (ii) H2O2-based alkene epoxidations, (iii) the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, (iv) liquid and gas-phase acid-catalyzed esterifications (acetic acid with n-butanol, methanol dehydration), and (v) and carbohydrate dehydration.